The central nervous system is a complex system of tissues, including cells, fluids and chemicals that interact in concert to enable a wide variety of functions, including movement, navigation, cognition, speech, vision and emotion. Unfortunately, a variety of debilitating malfunctions of the central nervous system may occur and disrupt some or all of these functions. These malfunctions are broad in range and include, for example, missing genetic elements, e.g., genetic diseases such as Tay-Sachs; malfunctioning cellular processes, e.g., Parkinson's Disease; trauma, e.g., head injury; degenerative diseases, e.g., Alzheimer's Disease; and damage due to lack of oxygen, e.g., caused by stroke or asphyxiation.
Typically, treatments for restoring central nervous system function after damage by the above malfunctions have been limited to drugs, and to adaptive or behavioral therapies. These approaches are generally limited in their ability to reverse damage (or stop degeneration) and restore normal function.
Recent research has explored the possibility of using cells to restore function to the central nervous system. Data using animal models suggests that cell implantation or transplantation may be an effective means for restoring central nervous system function after damage. Cells that have been used in this research have included various nonhematopoietic precursor cells, for example, fetal or embryonic neural cells from porcine and human sources (see, e.g., Nairne, S. P., Animal-to-Human transplants; the ethics of Xenotransplantation. London: Nuffield Council of Bioethics, 1996); immortalized fetal neural cells (Ren et al., Co-Administration of Neural Stem Cells and bFGF Enhances Functional Recovery Following Focal Cerebral Infarction in Rat, Soc. Neurosci. Abstr., 26:2291, 2000); mesenchymal bone marrow stem and progenitor cells (Chen et al., Intracerebral Transplantation with Cultured Bone Marrow Stroma Cells after MCAO in Rats, American Society for Neural Transplantation & Repair, Program and Abstracts, Volume 7: 2000, A-3) including multipotent adult stem cells (see, e.g., Keene et al., Phenotypic Expression of Transplanted Human Bone Marrow-Derived Multipotent Adult Stem Cells into the Rat CNS, American Society for Neural Transplantation & Repair, Program and Abstracts, Volume 7: 2000, 6-3); murine neural stem cells (Marciniak, Neural Stem Cells, In Combination with Basic FibroBlast Growth Factor (bFGF) May Represent a Treatment/or Stroke, supra, A-I), including immortalized murine neuroepithelial stem cells (Modo et al., Implantation Site of Stem Cells in MCAD Rats Influences the Recovery on Different Behavioral Tests, supra, 8-2); adult mouse and human neural stem and progenitor cells (see, e.g., Steindler et al., Stem Cells in the Human Brain, supra, 8-3); fetal mesencephalic cells (Mendez et al., Simultaneous Intraputaminal and Instranigral Fetal Dopaminergic Grafts in Parkinson's Disease: First Clinical Trials, supra, 5-3); testis-derived Sertoli cells (Cameron et al., Formation o/SNACs by Simulated Microgravity Coculture of Sertoli Cells and NT2 Cells. supra, C-), and crude bone marrow extract (Mahmood et al., Effects of Transplantation of Bone Marrow Cells on Wistar Rats Following Traumatic Brain Injury, supra, A-4). To overcome the lack of availability of many of these types of cells, researchers have even resorted to studying the possibility of administering cancer cells such as teratacarcinomal cells (Kondziolka et al., Transplantation of Cultured Human Neuronal Cells/or Patients with Stroke, Neurology 2000, 55: 565-569), despite the inherent dangers of the use of cancerous cells. Some research into cellular therapies has reached the clinical stage. Generally, the cells that have been used in the research described above pose potential hazards to patients, and/or are difficult to obtain.